Melatonin Timing Calculator

DLMO and the right time to take melatonin

The pineal gland begins putting out melatonin of its own at DLMO (Dim Light Melatonin Onset), roughly 2–3 hours before you naturally fall asleep, and the hormone peaks somewhere between 2:00 and 4:00. The estimate here uses DLMO ≈ bedtime − 2h. Example: with bedtime at 23:00, DLMO lands near 21:00. That is exactly the stretch when blue light from smartphones or white LEDs holds back the melatonin rise and pushes sleep later. If the goal is to advance the clock and fall asleep earlier, low doses of exogenous melatonin (0.5–3 mg) usually go in 2–4 hours before the bedtime you want, with a doctor's say-so, rather than at bedtime. In Brazil melatonin is cleared as a food supplement under ANVISA RDC 922/2024, up to 0.21 mg per dose for adults over 19.

Practical applications

Jet lag is the obvious one, and eastward trips get the most out of dosing ahead of bedtime. Beyond that, the same logic helps with shift-work disorder, primary insomnia, the delayed sleep phase that runs common in adolescents whose DLMO is naturally late, blind people stuck on non-24-hour rhythms, and commercial pilots juggling layovers. The effect grows stronger when the dose comes with dim lighting, no screens, and a warm bath in the hours before sleep. Take it right at bedtime and it behaves more like a sedative than a chronobiotic, doing nothing to shift the phase.

FAQ

Does taking 5 mg make me sleep more? No. Bigger doses tend to muddle the circadian effect and can leave you groggy the next morning, which is why sleep medicine usually points to 0.5–1 mg.

Can I use it every night? Using it for a few weeks is generally fine. For anything longer, talk to a doctor first, particularly if you're an adolescent or living with an autoimmune condition.

Does blue light really matter? It does. Sitting in 460-nm light for the 2 hours before bed can cut melatonin by as much as 50%. Warm-light filters or amber glasses help.

Children? Only with a specialist watching over it, in cases like autism or ADHD with disrupted sleep. RDC 922 limits over-the-counter sale to adults over 19 anyway.